"Pasta filata" refers to a type of cheese having a plastic pliable homogeneous stringy structure. The pasta filata cheeses are traditionally made by producing curds and whey, draining the whey and immersing the curd in hot water or hot whey and working, stretching and molding while it is in a plastic condition. The principal varieties of pasta filata cheeses are: Caciocavallo, Provolone, Provolette, Pizza Cheese, Mozzarella, Provole, Scamorze, and Provatura. The well known example of pasta filata-type of cheese is mozzarella. In the U.S., the standards of identity of the code of federal regulations subdivides mozzarella cheeses into: "Mozzarella", "Low Moisture Mozzarella", "Part Skim Mozzarella" and "Low Moisture Part Skim Mozzarella." In this specification when the term pasta filata or mozzarella is used in a generic sense, it is not capitalized. When it is used in a sense defined by the standards of identity, the term is capitalized. As defined by the FDA regulations, Mozzarella has a moisture content of more than 52 but not more than 60 weight percent and the fat in dry matter (FDM) of not less than 45 percent by weight. The Low Moisture Mozzarella has a moisture content of more than 45 but not more than 52 weight percent and FDM of not less than 45 weight percent. The Part Skim Mozzarella contains more than 52 but not more than 60 percent of moisture by weight and has the FDM of less than 45 but not less than 30 percent. The Low Moisture Part Skim Mozzarella contains more than 45 but not more than 52 percent of moisture by weight and has the FDM of less than 45 but not less than 30 percent.
One important use for pasta filata-type cheeses is as a topping for baked pizza. The most common type of pasta filata cheese used as a topping on baked pizzas is mozzarella, and in particular, Low Moisture Part-Skim Mozzarella. In fact, Low Moisture Part Skim Mozzarella is sometimes referred to as "pizza cheese".
Pasta filata-type cheese used as a pizza topping must possess certain functional characteristics. Specifically, the cheese must melt into a homogeneous mass without burning or blistering when subjected to pizza baking conditions. The cheese must possess acceptable level of stringiness when hot. The cheese must release sufficient amount of free oil to prevent surface burning of cheese during pizza baking. Finally, pock markings must be uniform, i.e., when heated the cheese must produce openings throughout to allow the sauce to go therethrough evenly.
In recent years the dairy industry has tried to increase the yield of cheese making processes by recovering the whey proteins in cheese. Several attempts have been made to produce pasta filata-type cheese that incorporates whey proteins. One method for producing "Pasta Filata" type cheese, which employs a step of ultrafiltration of milk is disclosed in U.S. Pat. No. 4,460,609 (Kristiansen et al.). According to the process of the Kristiansen et al. patent, pasta filata-type cheese is made by ultrafiltration of milk to produce a concentrate containing increased proportions of fat and proteins. An acid is added to the concentrate to coagulate it and to form a "cogel". Liquid is then separated from the "cogel" to increase the "cogel's" dry solids content. The cogel is then subjected to kneading and stretching. Since upon coagulation, the cogel undergoes syneresis, some of the whey proteins are lost in the separated liquid. Accordingly, the Kristiansen et al. process recovers in the cheese only part of the whey proteins that were originally present in the milk.
Another process developed by Pasilac Inc. for making mozzarella that incorporates whey protein by ultrafiltration is described in North European Dairy Journal (November, 1981) pp. 220-223. In the Pasilac process, milk is first standardized and pasteurized. Then the milk is acidified either microbiologically or chemically. The acidified milk is ultrafiltered to produce a retentate having a solids content corresponding to that of the final cheese. The lactose content of the retentate is adjusted by diafiltration. The retentate is then cooled to the culturing temperature. Lactic culture and rennet are added to convert the retentate into a cheese block. When the pH of the cheese block has reached the required value, the traditional mozzarella plasticization is carried out. The cheese block is stretched in hot water. The warm cheese mass is then molded into its final shape, cooled, salted and packed.
The above-described Pasilac process was claimed to increase the yield by about 18 percent over the traditional mozzarella making processes due to the recovery of whey proteins. However, attempts to commercialize the Pasilac process in the United States have failed because the process could not produce a product that would meet the necessary functional characteristics of mozzarella cheese. Specifically, the Pasilac cheese did not possess the necessary melt and stretch characteristics.
Another process using ultrafiltration of milk in the manufacture of mozzarella incorporating whey proteins was attempted and failed commercially in Denmark. As reported in North European Dairy Journal (March 1987), pp. 21-23, the Vesthimmerland dairy installed a mechanized ultrafiltration plant for the production of mozzarella having capacity of 5 tons per 24 hours. The cheese produced by this process did not meet the necessary functional characteristic for use on pizza and the plant had to be converted back to produce traditional mozzarella without whey proteins.
Thus, the prior attempts have been unsuccessful in devising an efficient, economical process that can produce pasta filata-type cheese incorporating high levels of soluble proteins, such as, whey proteins and having acceptable functional characteristics for use as cheese topping on baked pizza. There is, therefore, an unsatisfied, long-felt need for such product and for a process and system for making such a product.